THE ROOTSof Martin Sheen’s family tree are traced in the season premiere of the celebrity genealogy series “Who Do You Think You Are?” at 8 p.m. on NBC

SERIES

Nikita: Innocent lives hang in the balance when Percy (Xander Berkeley) has his Guardians take the members of Oversight hostage to force Amanda (Melinda Clarke) to give in to his demands. Dillon Casey, Maggie Q, Shane West and Lyndsy Fonseca also star in this new episode (8 p.m. KTLA).

Kitchen Nightmares: The owners of a contemporary American restaurant in Atlanta take pride in its diverse menu, but, as Gordon Ramsay discovers in this new episode, there’s a fine line between “diverse” and “disjointed” (8 p.m. Fox).Michael Feinstein’s American Songbook: The musical history series returns for a new season (9 p.m. KOCE).On Freddie Roach: Roach takes on U.S. Olympic boxing in this new episode (9:30 p.m. HBO).Spartacus: Vengeance: In this new episode, Spartacus (Liam McIntyre) and his men liberate a villa, but the slaves don’t welcome them with open arms in this new episode (10 p.m. Starz).Merlin: At Agravaine’s (Nathaniel Parker) urging, Arthur (Bradley James) kills King Caerleon (Steven Hartley), incurring the wrath of his widow, Queen Annis (Lindsay Duncan). He talks her into a trial by combat instead of war in this new episode (10 p.m. Syfy).

SPECIALS

Paul Mooney: The Godfather of Comedy: In this new stand-up special, the comedian turns his barbed wit on Sarah Palin, Tiger Woods, Mel Gibson and more (9 and 10:30 p.m. Showtime).

MOVIES

Gandhi: This 1982 biography garnered eight Academy Awards, including the prize for best picture. Richard Attenborough directed Ben Kingsley in the title role (5 p.m. TCM).